This invention relates to an ignition coil for internal combustion engines, and more particularly, to an ignition coil for internal combustion engines incorported in a distributor.
In, for example, Japanese Patent Publication No. 60--18834/1985, an ignition coil-incorporated distributor comprises a housing, a rotor shaft rotatably supported by the housing, a cap fitted to the housing, a distributor part including a rotor electrode mounted on a rotor top end of the rotor shaft and a side electrode mounted on the cap to face the rotor electrode with a gap therebetween. An ignition coil is secured to the housing, with a signal rotor being secured to the rotor shaft, and with a magnetic pickup for picking up signals and interrupting current flowing in a primary coil of the ignition coil according to the signal to cause a secondary coil of the ignition coil to induce a high voltage.
In the above noted ignition coil-incorporated distributor, the ignition coil is mounted on the housing at a position separated from the rotor shaft on one side by a sufficient distance through a screw means passing through a hole formed in a core of the ignition coil in a direction perpendicular to the axis of the rotor shaft.
Disadvantages of the above noted distributor resides in the fact that a portion of the distributor in which the ignition coil is provided projects sideways to thereby increasing the dimensions of the distributor. Moreover, the weight of the ignition coil having a winding wound around an iron core thereof and provided at a side portion of the housing represents a considerable percentage of a total weight of the distributor, so that the distributor becomes unstable with respect to the longitudinal axis thereof, and may create problems when mounted on a vehicle.
Furthermore, the ignition coil is fixed by screw means at right angles to the direction of the longitudinal axis of the distributor. Consequently, parts of the distributor are threadably secured in various directions thereby requiring a complicated distributor assembling operation, and corresponding decrease in the assembling efficiency.
Another example of the ignition coil-incorporated in, for example Japanese Patent Laid-Open No. 61--231708/1986, an ignition coil comprises an iron core constructed of various parts, that is, a cylindrical core axially elongated, a pair of cruciform cores disposed on upper and lower sides of the cylindrical core, respectively, and four radially extending arm portions, and plate-like cores at the tips of the arm portions to magnetically connect the upper and lower cruciform cores. Windings are wound around the cylindrical core through which a rotor shaft of the distributor passes with the ignition coil being mounted on the upper side of a bearing for supporting the rotor shaft.
Disadvantages of the last mentioned distributor resides in the fact that the iron core is very complicated. Further, and since the ignition coil is disposed at the upper side of the bearing for the rotor shaft, the size of the distributor increases in the direction of the longitudinal axis thereof by the height of the ignition coil. When the shaft is connected directly to a cam shaft in an engine, the distance between the bearings for the shaft decreases, so that the shaft shakes during the rotation thereof. This would cause interference of parts secured to the shaft with other parts facing the parts and generation of an unstable output signal.
When the last mentioned distributor is disposed laterally in an engine, that is, with the longitudinal axis of the distributor is disposed horizontal; the center of gravity thereof in the direction of the longitudinal axis thereof separates from the position in which the distributor is fixed to the engine resulting in, the distributor being readily vibrated thereby lowering the reliability of the strength thereof.